Effects of aluminum evaporator and 7 mm copper condenser coils on a 60,000 btu input packaged refrigeration system
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The purpose of this study was to determine the effect of aluminum evaporator coils and 7 mm copper condenser coils on a 60,000 Btu refrigeration unit. The development of this unit is due to a VAVE (value analysis and value engineering) effort, and the new design is significantly cheaper than the current design. New components are smaller and use mostly aluminum compared to copper; the heat transfer is significantly lower in aluminum, but other design improvements help in maintaining consistent performance. On the evaporator side, performance loss going from copper tubing to aluminum tubing will be made up by the lanced fins, which use the same material but have increased surface area. A blower which is intended for lower power usage increases efficiency and is designed with a new venture and scroll sides to maximize airflow. On the condenser side, the copper tube diameter is reduced from 3/8 inch to 9/32 inch and spacing between the tubes decreases from 1 inch to 0.8 inch. The performance loss due to this change is overcome by modified sub-cool loop circuits. The old design maintains certain AHRI (Air-Conditioning, Heating, and Refrigeration Institute) ratings which are met by the new cheaper model. The unit will be certified by CSA (Canadian Standards Association) to comply with safety standard UL-1995 and UL 60335-2-40. Unit has been tested for performance per standard AHRI 210/240. The refrigeration system is tested in a psychrometric test chamber while varying indoor and outdoor conditions. Thermocouples are used to measure sub-cool and superheat of the system and pressure taps are used to measure the suction pressure, discharge pressure and liquid pressure in the system. Given our test results, we developed a quality design which yielded us a higher capacity, better efficiency and lower cost. The 5 ton air-conditioning unit yielded us better performance than its predecessor model. Given the ease of manufacturability and performance numbers, it can be produced in large quantities and used in various parts of the world.
Thesis (M.S.)-- Wichita State University, College of Engineering, Dept. of Mechanical Engineering